Cook lasagna noodles "al dente.
Rinse with cold water and drain on paper towels.
In large bowl, mix together Ricotta cheese, most of the Mozzarella cheese (reserve enough to sprinkle over top), spinach and Parmesan cheese.
Preheat oven to 350°.
Pour a thin layer of spaghetti sauce in bottom of 13 x 9-inch pan.
Spread cheese and spinach mixture on each lasagna noodle, like spreading peanut butter.
Roll up lasagna noodles and arrange in pan.
Pour spaghetti sauce over all rolled lasagna noodles.
Top with reserved Mozzarella cheese.
Bake one hour.